Kohn anomaly and interplay of electron-electron and electron-phonon interactions in epitaxial graphene

TL;DR

This study investigates how electron-electron and electron-phonon interactions influence the electronic structure of epitaxial graphene, revealing the dominant role of the A1g phonon and the interplay between these interactions.

Contribution

It provides direct experimental evidence of the strong coupling between electrons and the A1g phonon in epitaxial graphene, highlighting the interplay of electron-electron and electron-phonon interactions.

Findings

Strong coupling of electrons to A1g phonon at 150 meV

Weak coupling to E2g phonon at 195 meV

Interplay of electron-electron and electron-phonon interactions affects self energy

Abstract

The interplay of electron-phonon (el-ph) and electron-electron (el-el) interactions in epitaxial graphene is studied by directly probing its electronic structure. We found a strong coupling of electrons to the soft part of the A1g phonon evident by a kink at 150+/-15 meV, while the coupling of electrons to another expected phonon E2g at 195 meV can only be barely detected. The possible role of the el-el interaction to account for the enhanced coupling of electrons to the A1g phonon, and the contribution of el-ph interaction to the linear imaginary part of the self energy at high binding energy are also discussed. Our results reveal the dominant role of the A1g phonon in the el-ph interaction in graphene, and highlight the important interplay of el-el and el-ph interactions in the self energy of graphene.